Vehicles can include cooling systems to remove waste heat from various systems and components, such as a vehicle engine. Such cooling systems can include a liquid coolant that is circulated through different components. For example, the coolant can be circulated through a radiator to allow the coolant to be cooled by a nearby fluid (such as air). The coolant can flow through a vehicle engine to allow heat to transfer from the engine to the coolant. The coolant can then flow through one or more heat exchangers to change temperature characteristics in one or more vehicle systems. For example, one of the heat exchanges can include a heater core that allows heat from the coolant to be transferred to nearby air flowing into a passenger compartment of the vehicle. Other heat exchanges can include accessory cooling components. For example, a heat exchanger can draw heat from a vehicle transmission. The warm coolant flowing through the heat core can provide undesired heating of the passenger compartment during which cool air is requested for the passenger compartment.